Courthouse Towers — Salt Beneath the Sandstone
Listen at the stop, then read the transcript and follow the sources behind the story.
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Transcript
The vertical towers here make the geology look like a story about sandstone. Much of the explanation lies deeper, in salt.
Hundreds of millions of years ago, evaporating seas left thick salt deposits in the region. Later sediments buried them. Salt behaves plastically under pressure, moving and deforming the rock above. Some salt structures later collapsed, creating valleys and zones of intense fracturing.
Those fractures gave erosion a map to follow. Once overlying layers were exposed, water and gravity enlarged the weaknesses into fins, towers and arches.
That is why Arches has such a dense concentration of unusual forms. The answer is not merely “soft rock plus erosion.” It is the specific combination of salt tectonics, jointed sandstone, uplift and an arid climate that preserves exposed forms long enough for us to see them.